Light-emitting device

ABSTRACT

A light-emitting device can be folded in such a manner that a flexible light-emitting panel is supported by a plurality of housings which are provided spaced from each other and the light-emitting panel is bent so that surfaces of adjacent housings are in contact with each other. Furthermore, in the light-emitting device, in which part or the whole of the housings have magnetism, the two adjacent housings can be fixed to each other by a magnetic force when the light-emitting device is used in a folded state.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to a light-emittingdevice. In particular, one embodiment of the present invention relatesto a light-emitting device using an electroluminescence (EL) phenomenon.Moreover, one embodiment of the present invention relates to a displaydevice.

Note that one embodiment of the present invention is not limited to theabove technical field. One embodiment of the invention disclosed in thisspecification and the like relates to an object, a method, or amanufacturing method. Moreover, one embodiment of the present inventionrelates to a process, a machine, manufacture, or a composition ofmatter. Specifically, examples of the technical field of one embodimentof the present invention disclosed in this specification include asemiconductor device, a display device, a light-emitting device, a powerstorage device, a storage device, an electronic device, a lightingdevice, an input device, an input/output device, a driving methodthereof, and a manufacturing method thereof.

In this specification and the like, a semiconductor device generallymeans a device that can function by utilizing semiconductorcharacteristics. Each of a semiconductor element such as a transistor, asemiconductor circuit, an arithmetic device, and a memory device is oneembodiment of a semiconductor device. An imaging device, a displaydevice, a liquid crystal display device, a light-emitting device, anelectro-optical device, a power generation device (including a thin filmsolar cell, an organic thin film solar cell, and the like), and anelectronic device may have a semi conductor device.

2. Description of the Related Art

Recent light-emitting devices and display devices are expected to beapplied to a variety of uses and become diversified.

For example, light-emitting devices and display devices for mobiledevices and the like are required to be thin, lightweight, and lesslikely to be broken.

The light-emitting device using an EL phenomenon (also referred to as anEL element) is thinned and lightened easily because a backlight which isnecessary for a liquid crystal display device is not needed. The ELelement also has features of, for example, high-speed response to aninput signal and driving with a direct-current low voltage source;therefore, its application to a light-emitting device and a displaydevice has been proposed.

For example, Patent Document 1 discloses a flexible active matrixlight-emitting device in which an organic EL element and a transistorserving as a switching element are provided over a film substrate.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2003-174153

SUMMARY OF THE INVENTION

In recent years, browsability of display has been improved by increasingthe amount of data to be displayed with an increase of a display regionof a display device. On the other hand, when mobile devices and the likewith a large-sized display regions have low portability; thus, it isdifficult to achieve improvement of display browsability and highportability together.

One object of one embodiment of the present invention is to provide alight-emitting device or the like having high portability. Anotherobject thereof is to provide a light-emitting device or the like havinghigh browsability. Another object thereof is to provide a light-emittingdevice or the like having high portability and browsability. Anotherobject thereof is to provide a novel display device or the like.

Note that the descriptions of these objects do not disturb the existenceof other objects. Note that in one embodiment of the present invention,there is no need to achieve all the objects. Objects other than theabove objects will be apparent from and can be derived from thedescription of the specification and the like.

According to one embodiment of the present invention, a light-emittingdevice includes a flexible light-emitting panel and a plurality ofhousings that support the light-emitting panel. The plurality ofhousings are spaced from each other, and two of the plurality ofhousings which face each other when the light-emitting panel is foldedare fixed to each other by magnetism.

It is preferable that each of the plurality of housings include aferromagnet and that the ferromagnet be provided in each of theplurality of housings so that magnetic poles of an upper surface and alower surface of the housing are opposite to each other and thatmagnetic poles of the upper surfaces of the two adjacent housings areopposite to each other.

Alternatively, the following structure is preferable: the plurality ofhousings are each any of a first housing including ferromagnets so thatmagnetic poles point to the upper surface and the lower surface of thehousing and a second housing including a soft magnetic substance thatmight be magnetized by the ferromagnet. The first housings and thesecond housings are alternately disposed. The first housing and thesecond housing which face each other when the light-emitting panel isfolded are fixed to each other by magnetism.

The soft magnetic substance preferably includes one or more selectedfrom Fe, an Fe—Ni alloy, an Fe—Si—Al alloy, and an Fe—Co alloy.

The ferromagnet preferably includes one or more selected from anisotropic ferrite magnet, an anisotropic ferrite magnet, a neodymiummagnet, a samarium cobalt magnet, and an alnico magnet.

In the case where the two housings which face each other are fixed toeach other when the light-emitting panel is folded, adsorption power ofthe two housings is preferably greater than or equal to 0.1 kgf and lessthan or equal to 2.0 kgf.

In any of the above structures, the following structure is preferable:in the case where the light-emitting panel is folded so that theadjacent housings are alternately overlapped to each other, a specifiedhousing between the two housings at ends of the plurality of housingscan be reversibly modified into a first mode in which the light-emittingpanel is folded so that the housing is located uppermost or a secondmode in which the light-emitting panel is folded so that the housing islocated lowermost.

Note that the light-emitting device in this specification includes, inits category, a light source (including a lighting device) or the likein addition to a display device using a light-emitting element. Inaddition, the light-emitting device might include any of the followingmodules in its category: a module in which a connector such as aflexible printed circuit (FPC) or a tape carrier package (TCP) isattached to a light-emitting device; a module having a TCP provided witha printed wiring board at the end thereof; and a module having anintegrated circuit (IC) directly mounted on a substrate over which alight-emitting element is formed by a chip on glass (COG) method.

According to one embodiment of the present invention, a light-emittingdevice having high portability can be provided. Alternatively, alight-emitting device having high browsability can be provided. Furtheralternatively, a light-emitting device haying high portability andbrowsability can be provided. Note that one embodiment of the presentinvention is not limited to these effects. For example, depending oncircumstances or conditions, one embodiment of the present inventionmight produce another effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C each illustrate a structural example of a light-emittingdevice of an embodiment.

FIG. 2 illustrates a structural example of a light-emitting device of anembodiment.

FIGS. 3A1 and 3A2, 3B1 and 3B2, and 3C illustrate a structural exampleof a light-emitting device of an embodiment.

FIGS. 4A1 and 4A2, 4B1 and 4B2, and 4C1 and 4C2 illustrate structuralexamples of a light-emitting device of an embodiment.

FIGS. 5A1 and 5A2 and 5B1 and 5B2 illustrate structural examples of alight-emitting device of an embodiment.

FIGS. 6A to 6C illustrate a structural example of a light-emittingdevice of an embodiment.

FIG. 7 illustrates a structural example of a light-emitting device of anembodiment.

FIGS. 8A to 8C each illustrate a structural example of a light-emittingdevice of an embodiment.

FIGS. 9A and 9B illustrate a light-emitting panel of an embodiment.

FIGS. 10A and 10B each illustrate a light-emitting panel of anembodiment.

FIGS. 11A and 11B each illustrate a light-emitting panel of anembodiment.

FIGS. 12A and 12B illustrate a light-emitting panel of an embodiment.

FIGS. 13A to 13C illustrate an example of a method for manufacturing alight-emitting panel of an embodiment.

FIGS. 14A to 14C illustrate an example of a method for manufacturing alight-emitting panel of an embodiment.

FIG. 15 illustrates a light-emitting panel of an embodiment.

FIGS. 16A and 16B each illustrate a structural example of alight-emitting device of an embodiment.

FIGS. 17A to 17C illustrate an example of an electronic device.

FIGS. 18A1 and 18A2, 18B1 and 18B2, and 18C illustrate a structuralexample of a light-emitting device of an embodiment.

FIGS. 19A and 19B each illustrate a structural example of alight-emitting device of an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to drawings. Notethat the present invention is not limited to the description below, andit is easily understood by those skilled in the art that various changesand modifications can be made without departing from the spirit andscope of the present invention. Accordingly, the present inventionshould not be interpreted as being limited to the content of theembodiments below.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Furthermore, the same hatching pattern isapplied to portions having similar functions, and the portions are notespecially denoted by reference numerals in some cases.

Note that in each drawing described in this specification, the size, thelayer thickness, or the region of each component is exaggerated forclarity in some cases. Therefore, embodiments of the present inventionare not limited to such a scale.

Note that in this specification and the like, ordinal numbers such as“first”, “second”, and the like are used in order to avoid confusionamong components and do not limit the number.

Embodiment 1

In this embodiment, a light-emitting device of one embodiment of thepresent invention will be described with reference to drawings.

In a light-emitting device of one embodiment of the present invention, aflexible light-emitting panel is supported by a plurality of housingswhich are provided spaced from each other. In the light-emitting device,the light-emitting panel can be bent at a portion. between the twoadjacent housings. The light-emitting device can be folded by bendingthe light-emitting panel so that surfaces of adjacent housings face eachother. A light-emitting device of one embodiment of the presentinvention is highly portable in a folded state, and has highbrowsability in display in an opened state because of a seamless largelight-emitting region (display region).

Moreover, in the light-emitting device of one embodiment of the presentinvention, in which part or the whole of the housings have magnetism,the two adjacent housings can be fixed to each other by a magnetic forcewhen the light-emitting device is used in a folded state. Therefore, amechanical jig for fixing the housings is not necessary; therefore, thedesign can be simplified and the number of components can be reduced.

Since the two housings are fixed to each other by a magnetic force,gravitation is generated only when adjacent housings get close to eachother by bending the light-emitting panel at a time when thelight-emitting device is modified from the opened state to the foldedstate. Therefore, bending or twisting of the light-emitting panel in anunintentional direction when the light-emitting device is modified fromthe opened state to the folded state can be prevented; thus, damage ofthe light-emitting panel can be suppressed. On the other hand, forexample, in a structure where two housings are fixed to each other witha fixing jig or the like after the light-emitting panel is bent by auser so that the housings are in contact with each other, thelight-emitting panel that connects the two housings with each othermight be damaged due to a curve with a curvature radius of thespecification limit or lower or twisting of the light-emitting panel inan unintentional direction.

Moreover, the gravitation generated by magnetism is in inverseproportion to the square of the distance between two housings;therefore, when the light-emitting device is modified from the foldedstate to the opened state, the two housings can be easily separated fromeach other by inserting a finger or the like into a space between thetwo fixed housings to make a small gap therebetween. Therefore, anoperation of separating the two housings by, for example, pulling thetwo fixed housings in the opposite directions is not needed.Accordingly, the light-emitting panel, which connects the two housingswith each other, can be prevented from being damaged due to carelesspulling of the housings.

In the light-emitting device of one embodiment of the present invention,the light-emitting panel can be bent either inward or outward.

Note that in this specification, “being bent inward” means being bentsuch that a light-emitting surface of a light-emitting panel facesinward, and “being bent outward” means being bent such that alight-emitting surface of a light-emitting panel faces outward. Alight-emitting surface of a light-emitting panel or a light-emittingdevice refers to a surface through which light emitted from alight-emitting element is extracted.

When the light-emitting device of one embodiment of the presentinvention is bent such that a light-emitting surface of thelight-emitting panel faces inward, the light-emitting surface can beprevented from being damaged or contaminated in carrying thelight-emitting device. This is preferable, for example, in carrying thelight-emitting device in a pocket of clothes or a bag.

When the light-emitting device of one embodiment of the presentinvention is in use, the seamless large light-emitting region isentirely used in an opened state, or the light-emitting region can bepartly used by bending such that the light-emitting surface of thelight-emitting panel faces outward. Inward folding of the light-emittingdevice can reduce the power consumption because part of thelight-emitting region that is hidden from a user becomes anon-light-emitting region.

STRUCTURAL EXAMPLE

The following shows structural examples of a light-emitting device ofone embodiment of the present invention. As an example, described belowis a light-emitting device in which a flexible light-emitting panel issupported by three housings and is curved at two places so that thelight-emitting device can be modified from the opened state to thethree-folded state.

FIG. 1A illustrates a light-emitting device 100 that is opened. FIG. 1Billustrates the light-emitting device 100 that is being opened or beingfolded. FIG. 1C illustrates the light-emitting device 100 that isfolded. FIG. 2 is a development view illustrating components of thelight-emitting device 100.

The light-emitting device 100 includes a flexible light-emitting panel101. The light-emitting device 100 also includes a plurality of housings(housings 111, 112, and 113). The plurality of housings are separatedfrom one another. Note that in the case of describing common points ofthe housings 111, 112, and 113 without distinguishing from one another,they are in some cases simply referred to as the housings.

Each housing may support the light-emitting panel 101 and may beprovided on at least one of the light-emitting surface side and the sideopposite to the light-emitting surface side (also referred to as a lowersurface side or a rear surface side) of the light-emitting panel. FIGS.1A to 1C and FIG. 2 illustrate an example of the housings that supportthe outer edge on the light-emitting surface side of the light-emittingpanel 101 and the side opposite to the light-emitting surface side ofthe light-emitting panel 101. With the housings that support both sidesof the light-emitting panel 101, the mechanical strength of thelight-emitting panel 101 can be increased, whereby the light-emittingdevice 100 can be prevented from being damaged.

Each housing may have rigidity or may be formed with a member capable ofbeing modified with respect to force such as bending and twisting. Eachhousing may be formed with a material having lower flexibility than atleast the light-emitting panel 101, and an elastic body such as hardrubber may be used for a skeleton of the housing. Besides, as a materialthat constitutes each housing, plastic, a metal such as aluminum, analloy such as stainless steel or a titanium alloy, rubber such assilicone rubber, or the like can be used.

In addition, as illustrated in FIGS. 1A to 1C and FIG. 2, it ispreferable to provide a protective layer 102 that supports the sideopposite to the light-emitting surface side of the light-emitting panel101 and the outer edge on the light-emitting surface side thereof. Evenin the case where the mechanical strength of the light-emitting panel101 itself is low, the mechanical strength at a curved portion can beincreased by the protective layer 102. Note that although here, theprotective layer 102 is provided to entirely cover the light-emittingpanel 101, the protective layer 102 may be provided in at least portionseach between two housings, that is, a curved region. As illustrated inFIG. 2, the light-emitting panel 101 is sandwiched between the twoprotective layers 102 and is disposed so as to place at the centerportion with respect to the thickness directions of the protectivelayers 102, whereby stress applied to the light-emitting panel 101 whenthe light-emitting panel 101 and the protective layers 102 are curvedinward or outward can be suppressed to be as little as possible.

It is preferable that the protective layer 102 on the light-emittingsurface side be provided with an opening overlapping with thelight-emitting region of the light-emitting panel 101 and be provided tocover the peripheral portion of the light-emitting panel 101.Alternatively, the protective layer 102 provided with alight-transmitting member overlapping with the light-emitting region maybe used. For example, when the protective layer 102 is provided so as tocover a wiring, a driver circuit, or the like positioned at an endportion of the light-emitting panel 101, the wiring, the driver circuit,or the like can be physically protected and the light-emitting panel 101can be prevented from deteriorating because the wiring, the drivercircuit, or the like is shielded from light. Furthermore, the wiring,the driver circuit, or the like can be prevented from being viewed inwhich case visual pleasure of the light-emitting device itself isimpeded.

For example, plastic, rubber, a metal, an alloy, or the like can be usedfor the protective layer 102.

Plastic, rubber, a titanium alloy, or the like is preferably used forthe protective layer 102 and the housing because the light-emittingdevice can be lightweight and less likely to be broken.

The protective layer 102 and the housing are preferably formed using amaterial with high toughness. Thus, a light-emitting device with highimpact resistance that is less likely to be broken can be provided. Forexample, when an organic resin, a thin metal material, or a thin alloymaterial is used, the light-emitting device can be lightweight and lesslikely to be broken. For a similar reason, also a substrate of thelight-emitting panel 101 is preferably formed using a material with hightoughness.

The protective layer 102 and the housing on the light-emitting surfaceside do not necessarily have a light-transmitting property if they donot overlap with the light-emitting region of the light-emitting panel101. When the protective layer 102 and the housing on the light-emittingsurface side overlap with at least part of the light-emitting region,they are preferably formed using a material that transmits light emittedfrom the light-emitting panel 101. There is no limitation on thelight-transmitting property of the protective layer 102 and the housingon the side opposite to the light-emitting surface side.

When any two of the protective layer 102, the housing, and thelight-emitting panel 101 are bonded to each other, any of a variety ofadhesives can be used. For example, a resin that is curable at roomtemperature such as a two-component-mixture-type resin, a light-curableresin, a thermosetting resin, or the like can be used. Alternatively, asheet-like adhesive may be used. Alternatively, components of thelight-emitting device may be fixed with, for example, a screw thatpenetrates two or more of the protective layer 102, the housing, and thelight-emitting panel 101 or a pin or clip that holds them.

The light-emitting device of one embodiment of the present invention canbe used with one light-emitting panel 101 (one light-emitting region)divided into two or more regions at a folded portion(s). For example, itis possible to put the region that is hidden by folding thelight-emitting device in a non-light-emitting state and put only theexposed region in a light-emitting state. Thus, power consumed by aregion that is not viewed by a user can be reduced.

The light-emitting device of one embodiment of the present invention mayinclude a sensor for determining whether the light-emitting panel 101located between the housings is curved or not. For example, the sensorcan be composed of, for example, a switch, a MEMS pressure sensor, apressure sensor, or the like.

In the light-emitting device of one embodiment of the present invention,a flexible touch sensor may be provided so as to overlap with thelight-emitting panel 101. Preferably, the touch sensor is provided sothat a detection surface of the touch sensor is located on the displaysurface side of the light-emitting panel 101. At this time, when thelight-emitting panel 101 is bent, the detection surface of the touchsensor is preferably bent along a curved surface made by the displaysurface of the display panel 101.

Note that a touch parcel that functions as a touch sensor may be used asthe light-emitting panel 101.

By folding the light-emitting device 100 at a portion between thehousings, the light-emitting device 100 can be reversibly modified fromthe developed state in FIG. 1A to the folded state in FIG. 1C through astate in FIG. 1B. At this time, the relative positions between thehousing 111 and the housing 112 and between the housing 112 and thehousing 113 are fixed by a magnetic force.

[Fixing Method of Housings by Magnetic Force]

Next, an example of a method for fixing the relative position of thehousings by a magnetic force when the light-emitting device is folded isdescribed.

FIG. 3A1 is a top view of the light-emitting device, and FIG. 3A2 is arear view of the light-emitting device. FIG. 3B1 is a schematic sideview of a range A-B when viewed in the direction indicated by an arrowin FIG. 3A1, and FIG. 3B2 is a schematic cross-sectional view takenalong line C-D in FIG. 3A1. FIG. 3C is a schematic side view of therange A-B when viewed in the direction indicated by the arrow in FIG.3A1 in a state where the light-emitting device is folded. Note that thethickness of the light-emitting panel 101 is exaggerated for clarity inFIG. 3B2.

The light-emitting device illustrated in FIGS. 3A1 to 3C includes thehousings 111, 112, and 113 whose surfaces are magnetized. The uppersurface and the lower surface of the housing are provided with fernmagnets, which are magnetized, so that magnetic poles of the uppersurface and the lower surface of the housing are opposite to each other.Furthermore, the ferromagnets are magnetized so that magnetic poles ofthe upper surfaces of the two adjacent housings are opposite to eachother. Therefore, the ferromagnets are similarly magnetized so thatmagnetic poles of the lower surfaces of the two adjacent housings areopposite to each other.

Note that in the following description, a surface of the housing on thelight-emitting surface side is described as an upper surface and asurface thereof on the opposite side is described as a lower surface.

Here, as an example, the ferromagnets provided on the upper surface ofthe housing 111, the lower surface of the housing 112, and the uppersurface of the housing 113 are magnetized to be N poles, and theferromagnets provided on the lower surface of the housing 111, the uppersurface of the housing 112, and the lower surface of the housing 113 aremagnetized to be S poles. Needless to say, the N poles and S poles maybe switched to each other.

With such a structure, as illustrated in FIG. 3C, magnetic poles of thelower surface of the housing 111 and the lower surface of the housing112 (upward surfaces in FIG. 3C) that face each other when thelight-emitting device is folded are opposite to each other; therefore,the two housings are attracted and fixed to each other. In a similarmanner, with the upper surface of the housing 112 (a downward surface inFIG. 3C) and the upper surface of the housing 113, the two housings arefixed to each other by gravitation.

Here, as a ferromagnet, a material including an isotropic ferritemagnet, an anisotropic ferrite magnet, a neodymium magnet (Nd—Fe—B), asamarium cobalt magnet (Sm—Co), or an alnico magnet (Fe—Al—Ni—Co) can beused, for example. Moreover, as a ferromagnet, a rubber magnet in whicha powdery magnet or the like is mixed into rubber, a plastic magnet inwhich a powdery magnet or the like is mixed into plastic, or the likemay be used. Such a magnet is referred to as a bond magnet or a bondedmagnet.

In particular, when the above bonded magnet is used in the case wherethe housing surfaces are magnetized, the weights of the housings can bereduced and the housings can be easily processed into arbitrary shapes.After such a material is used for the housings and is processed, thehousing surfaces may be magnetized so that magnetic poles point to thehousing surface in the above directions.

With such a structure in which the two adjacent housings are fixed toeach other by two ferromagnets facing each other, the two ferromagnetsare each influenced by their magnetic fields when the two housings areoverlapped with each other; therefore, demagnetization of theferromagnets influenced by the external magnetic field can be reduced insome cases.

Although the upper surfaces themselves of the housings are magnetized byproviding the ferromagnets on the upper surfaces of the housings in theabove example, a ferromagnet may be disposed inside the housing in thevicinity of the upper surface or the lower surface of the housing asillustrated in FIGS. 4A1 and 4A2. Here, FIG. 4A1 illustrates the topview and the rear view of the light-emitting device which corresponds toFIGS. 3A1 and 3A2, and FIG. 4A2 is a schematic cross-sectional viewtaken along line E-F in FIG. 4A1.

Note that for clarity, in FIG. 4A2, a ferromagnet disposed so that an Npole points in a direction perpendicular to the surface of a housing isdenoted by N, and a ferromagnet disposed so that an S pole points in adirection perpendicular to the surface of a housing is denoted by S. Thesame material or a different material may be used for the ferromagnetsas long as the magnetic poles are different.

At this time, a material having a low magnetic permeability ispreferably used for the housings.

With such a structure, it is possible to use plastic, glass, ceramic,rubber, a metal or an alloy having a low magnetic permeability, or thelike as materials of the housings, which is preferable because materialsof the housings can be selected more freely.

As illustrated in FIGS. 4B1 and 4B2, a ferromagnet may be disposed inpart of the housing instead of the whole of the housing. At this time,it is preferable to dispose two or more ferromagnets on one surface of ahousing so that the ferromagnets are apart from each other. When twohousings are provided so as to face each other, the ferromagnetsprovided for the housings are attracted to each other at two or moreplaces, whereby the relative position of the two housings in a planebetween the housing surfaces parallel to each other are fixed andaccordingly two-dimensional positional deviation of the two housings canbe solved effectively.

Moreover, in the case where ferromagnets are disposed in part of thehousings, use of a material having high magnetic flux density (orresidual magnetic flux density) for the ferromagnets is preferable todisposition of the ferromagnets on the entire surfaces of the housingsbecause an area where the two ferromagnets face each other becomes smallwhen the light-emitting device is folded.

Ferromagnets to be used may be selected in consideration of magneticflux density of materials depending on an area where the twoferromagnets face each other and a distance between the two ferromagnetswhen the two housings are overlapped with each other. For example, thegravitation between the ferromagnets becomes stronger as the area wherethe two ferromagnets face each other gets larger or the distance betweenthe two ferromagnets gets shorter; therefore, a material having lowmagnetic flux density can be used. In that case, the magnetic fluxdensity of the ferromagnet may be less than 100 mT. Moreover, in thecase where a ferromagnet having high magnetic flux density needs to beused, a ferromagnet having magnetic flux density of 100 mT or more, 200mT or more, or 500 mT or more can be used. for example.

For example, when two housings are overlapped with each other, powernecessary to separate the two housings is determined depending on thearea where the ferromagnets face each other and magnetic flux density ofeach ferromagnet. It is preferable to determine as appropriate thematerial (magnetic flux density) of the ferromagnets disposed on thehousing or the area where the two ferromagnets face each other so thatpower necessary to separate the two housings (also referred to asadsorption power) becomes greater than or equal to 0.1 kgf and less thanor equal to 2.0 kgf, preferably greater than or equal to 0.2 kgf andless than or equal to 1.0 kgf. In such a range, the two housings can besurely fixed to each other when the light-emitting device is folded andthe two housings can be easily separated from each other when thelight-emitting device is developed. For example, when the adsorptionpower of the two housings is less than 0.05 kgf, the two housings mightnot be fixed surely. On the other hand, when the adsorption power of thetwo housings is greater than the upper limit of the above range,attracting force between the two housings is increased and it might bedifficult to easily separate the two housings from each other.

As illustrated in FIGS. 4C1 and 4C2, a structure in which a recessedportion is provided on the housing surface and a ferromagnet is providedat the bottom of the recessed portion may be employed. When the twohousings are thus overlapped with each other, the gravitation betweenthe two ferromagnets can be increased because there is no member thatconstitutes a housing between the two ferromagnets facing each other.Moreover, with such a structure in which a position of the ferromagnetcan be viewed by a user, it is possible to prevent a defect in which thetwo housings cannot be fixed to each other due to, for example,insertion of a material having high magnetic permeability between thetwo ferromagnets by mistake. Note that the recessed portion provided forthe housing may be filled or covered with a material having lowermagnetic permeability or a material having higher light-transmittingproperty than a member of the housing.

MODIFICATION EXAMPLE 1

Although the position of the two housings are fixed to each other byproviding the ferromagnets on the adjacent housings and utilizing amagnetic force between the two ferromagnets in the above example, one ofthe ferromagnets may be replaced with a soft magnetic substance.

In other words, the plurality of housings each may include a ferromagnetso that magnetic poles point to the upper surface and the lower surfaceof the housing or a soft magnetic substance that might be magnetized bythe ferromagnet. The housings including the ferromagnet and the housingsincluding the soft magnetic substance may be alternately disposed.

FIGS. 5A1 and 5A2 illustrate the structure in FIGS. 4B1 and 4B2 in whichthe ferromagnets in the housings 111 and 113 are replaced with softmagnetic substances 122. At this time, the direction of a magnetic poleof the ferromagnet provided for the housing 112 is not limited;therefore, the ferromagnet is illustrated with the same hatching patternas a ferromagnet 121.

As a material of the soft magnetic substance 122, a material having highmagnetic permeability can be used; for example, a material including asoft magnetic substance such as Fe, an Fe—Ni alloy, an Fe—Si—Al alloy,or an Fe—Co alloy can be used.

Under ideal conditions, attracting force between the ferromagnet and thesoft magnetic substance is almost half attracting force between twoferromagnets. Therefore, a material used for the ferromagnet preferablyhas higher magnetic flux density than a material used for a pair offerromagnets described above.

Note that although FIGS. 5A1 and 5A2 illustrate the structure in FIGS.4B1 and 4B2 in which the ferromagnets in the housings 111 and 113 arereplaced with the soft magnetic substances 122, one embodiment of thepresent invention is not limited thereto. For example, as illustrated inFIGS. 5B1 and 5B2, the ferromagnets in the housing 112 may be replacedwith the soft magnetic substances 122. Alternatively, the ferromagnet inone housing of the adjacent housings in the structure illustrated inFIGS. 3A1 to 3C or another structure in FIGS. 4A1 to 4C2 may be replacedwith the soft magnetic substance 122 as illustrated in FIGS. 18A1 to18C. Further alternatively, when a mixture of the ferromagnet 121 andthe soft magnetic substance 122 is provided for one housing and the twoadjacent housings are overlapped with each other, the ferromagnet 121and the soft magnetic substance 122 may be disposed so as to face eachother.

Instead of the soft magnetic substance 122, a soft magnetic substancematerial may be used for part of a region of the surface or the vicinityof the surface of the housing.

MODIFICATION EXAMPLE 2

Although the ferromagnets and the soft magnetic substances are disposedalong the upper surface or the lower surface of the housing in the aboveexample, they may be provided at the side of the housing.

FIGS. 6A to 6C illustrate a structural example of a light-emittingdevice described below. FIG. 6A is a schematic top view in a developedstate of the light-emitting device, FIG. 6B is a schematiccross-sectional view taken along line G-H in FIG. 6A, and FIG. 6C is aschematic cross-sectional view in a folded state of the light-emittingdevice.

In the structure illustrated in FIGS. 6A to 6C, the ferromagnet 121 isdisposed inside the housing 112 along the side surface of the housing112 (a surface perpendicular to the light-emitting surface of thelight-emitting panel 101).

When the light-emitting device is folded as illustrated in FIG. 6C, thesoft magnetic substance 122 is disposed on the housings 111 and 113overlapping with the ferromagnet 121 in the housing 112.

Note that at least one of the ferromagnet 121 and the soil magneticsubstance 122 may be exposed to the outside of the housings.

At this time, the magnetic poles of the ferromagnet 121 are preferablyaligned in a direction perpendicular to the light-emitting surface. Themagnetic poles of the ferromagnet 121 are preferably aligned in adirection perpendicular to the light-emitting surface, in which case theattracting force between the ferromagnet 121 and the soft magneticsubstance 122 is increased. On the other hand, when the attracting forcebetween the ferromagnet 121 and the soft magnetic substance 122 are toohigh, the direction of the magnetic poles of the ferromagnet 121 isdeviated from the direction perpendicular to the light-emitting surface,so that the attracting force can be controlled to be low.

By thus disposing the ferromagnet 121 in the vicinity of the sidesurface of the housing, the thickness of the housing can be drasticallyreduced as compared with the case where the two ferromagnets 121 aredisposed along the upper surface and the lower surface of the housing.In the light-emitting device of one embodiment of the present inventionwhich can be particularly used in a folded state, a reduction in thethickness of the housing leads to a reduction in the thickness in thefolded state; therefore, portability of the light-emitting device can befurther improved.

Note that although the ferromagnet 121 is provided here for the housing112, the ferromagnet 121 may be provided for the housings 111 and 113and a soft magnetic substance may be provided for the housing 112.Alternatively, the ferromagnet 121 may be provided in the vicinities ofthe side surfaces of the three housings so that magnetic poles of thethree housings are opposite to each other when the light-emitting deviceis folded.

The above is the description of the modification examples.

In any of the above light-emitting devices of embodiments of the presentinvention, in common, even when a portion of the light-emitting panel101 between two housings is bent either inward or outward, the twohousings can be fixed to each other by a magnetic force.

Therefore, as illustrated in, for example, FIG. 7, a mode X in adeveloped state of the light-emitting device as a starting point can bereversibly modified into a mode Y2 in which the housing 111 is locateduppermost and the housing 113 is located lowermost through a mode Y1 inwhich a portion between the housing 111 and the housing 112 is bentoutward and a portion between the housing 112 and the housing 113 isbent inward. On the other hand, the mode X as a starting point can bereversibly modified into a mode Z2 in which the housing 111 is locatedlowermost and the housing 113 is located uppermost through a mode Z1 inwhich the portion between the housing 111 and the housing 112 is bentinward and the portion between the housing 112 and the housing 113 isbent outward.

Here, in either the mode Y2 or the mode Z2 in FIG. 7, the relativeposition of the two adjacent housings is fixed by a magnetic force.

In other words, in the case where the light-emitting panel of thelight-emitting device of one embodiment of the present invention isfolded so that the adjacent housings are alternately overlapped to eachother, a specified housing between the two housings at ends of theplurality of housings can be reversibly modified into a state in whichthe light-emitting panel is folded so that the housing is locateduppermost or a state in which the light-emitting panel is folded so thatthe housing is located lowermost.

Note that one embodiment of the present invention is not limited to thisstructure. All display panels may be bent inward and the plurality ofhousings may be fixed. For example, FIGS. 16A and 16B illustrate anexample of the structure in FIG. 3C in which the plurality of housingsare fixed so that all the display panels are bent inward. Even in thecase of bending all the display panels inward like this or bending allthem outward, the light-emitting device can be appropriately fixedbecause the directions of the magnetic poles of the ferromagnets accordwith each other.

Note that in the case where a display device is not used (in the casewhere an image is not displayed), all the display panels are preferablybent inward and fixed as illustrated in FIGS. 16A and 16B. Accordingly,the display device can be protected from damage because the uppersurface of the display device is not exposed. Therefore, even when thelight-emitting device is put in a bag or a pocket, it can be put in acompact way. Moreover, in the case inhere the display device is used,display can be made even in a folded state by fixing the display panelsas illustrated in FIG. 3C. Note that one embodiment of the presentinvention is not limited thereto.

Note that although examples in which the three-foldable light-emittingdevice including the three housings are described above, the number ofhousings is not limited thereto. For example, each of a two-foldablelight-emitting device including two housings 110 illustrated in FIG. 8A,a four-foldable light-emitting device including four housings 110illustrated in FIG. 8B, and a five-foldable light-emitting deviceincluding five housings 110 illustrated in FIG. 8C is also oneembodiment of the present invention. Alternatively, the number ofhousings 110 may be six or more.

Although the structure in which the portions between the two housingsare connected to each other by the protective layers 102 is describedabove, the portions between the two housings may be mechanicallyconnected to each other by hinges. Relative movable ranges of theportions between the two housings can be controlled by hinges;therefore, the light-emitting panel 101 can be prevented from beingbroken.

Electronic components, for example, a battery, a printed circuit boardon which various ICs such as an arithmetic unit and a driver circuit aremounted, a wireless receiver, a wireless transmitter, a wireless powerreception, and various sensors such as an acceleration sensor areincorporated, as appropriate, into housing of the light-emitting deviceof one embodiment of the present invention, so that the light-emittingdevice can function as an electronic device such as a portable terminal,a portable image reproducing device, or a portable lighting device. Atthis lime, each electronic component may be collectively provided forany one of the plurality of housings. Alternatively, electric componentsmay be dispersively provided for the plurality of housings toelectrically connect the electronic components in the plurality ofhousings to each other by a wiring sandwiched between the protectivelayers 102 or a wiring or the like provided in the protective layer 102.Further alternatively, various input/output terminals including acamera, a speaker, and a power supply potential; various sensorsincluding an optical sensor and the like; an operation button; or thelike may be incorporated into the housing of the light-emitting device.

Although the thicknesses of the plurality of housings illustrated in thedrawings are almost the same in the above drawings, the thickness ofeach housing may be different without limitation thereto. It ispreferable that the thicknesses of two or more housings, preferably thethicknesses of all the housings be almost the same, in which casehorizontality of the light-emitting surface in the developed state ofthe light-emitting device can be held easily. Alternatively, one of theplurality of housings is used as a main body having a relative largethickness in which all or most of the above electronic components arecollectively provided for the housing and the other housings havinglower thicknesses are used as members for supporting the light-emittingpanel 101.

Note that an example in which the light-emitting element is used as adisplay element is illustrated, one embodiment of the present inventionis not limited to such an example.

For example, in this specification and the like, a display element, adisplay device which is a device including a display element, alight-emitting element, and a light-emitting device which is a deviceincluding a light-emitting element can employ various modes or caninclude various elements. Examples of a display element, a displaydevice, a light-emitting element, or a light-emitting device include anEL (electroluminescent) element (e.g., an EL element including organicand inorganic materials, an organic EL element, or an inorganic ELelement), an LED (e.g., a white LED, a red LED, a green LED, or a blueLED), a transistor (a transistor which emits light depending oncurrent), an electron emitter, a liquid crystal element, electronic ink,an electrophoretic element, a grating light valve (GLV), a plasmadisplay panel (PDP), a micro electro mechanical system (MEMS), a digitalmicromirror device (DMD), a digital micro shutter (DMS), aninterferometric modulator display (IMOD) element, an electrowettingelement, a piezoelectric ceramic display, or a carbon nanotube, whichare display media whose contrast, luminance, reflectivity,transmittance, or the like is changed by electromagnetic action. Notethat examples of a display device having an EL element include an ELdisplay and the like. Display devices having electron emitters include afield emission display (FED), an SED-type flat panel display (SED:surface-conduction electron-emitter display), and the like. Examples ofa display device having a liquid crystal element include a liquidcrystal display (e.g., a transmissive liquid crystal display, atransflective liquid crystal display, a reflective liquid crystaldisplay, a direct-view liquid crystal display, or a projection liquidcrystal display) and the like. Examples of a display device having anelectronic ink or electrophoretic element include electronic paper.

For example, in this specification and the like, an active matrix methodin which an active element is included in a pixel or a passive matrixmethod in which an active element is not included in a pixel can beused.

In the active matrix method, as an active element (a non-linearelement), not only a transistor but also various active elements(non-linear elements), for example, a MIM (metal insulator metal), a TFD(thin film diode), or the like can be used. Since such an element hasfew numbers of manufacturing steps, manufacturing cost can be reduced oryield can be improved. Alternatively, since the size of the element issmall, the aperture ratio can be improved, so that power consumption canbe reduced or higher luminance can be achieved.

Note that as a method other than an active matrix method, a passivematrix method in which an active element (a non-linear element) is notused can also be used. Since an active element (a non-linear element) isnot used, the number of manufacturing steps is small, so thatmanufacturing cost can be reduced or yield can be improved.Alternatively, since an active element (a non-linear element) is notused, the aperture ratio can be improved, so that power consumption canbe reduced or higher luminance can be achieved, for example.

At least part of this embodiment can be implemented as appropriate incombination with any of the other embodiments described in thisspecification.

Embodiment 2

In this embodiment, a light-emitting panel will be described withreference to drawings.

SPECIFIC EXAMPLE 1

FIG. 9A is a plan view of the light-emitting panel 101 described as anexample in Embodiment 1, and FIG. 9B is an example of a cross-sectionalview taken along dashed-dotted line A1-A2 in FIG. 9A.

The light-emitting panel illustrated in FIG. 9B includes an elementlayer 501, a bonding layer 505, and a substrate 503. The element layer501 includes a substrate 201, a bonding layer 203, an insulating layer205, a plurality of transistors, a conductive layer 557, an insulatinglayer 207, an insulating layer 209, a plurality of light-emittingelements, an insulating layer 211, a sealing layer 213, an insulatinglayer 261, a coloring layer 259, a light-blocking layer 257, and aninsulating layer 255.

The conductive layer 557 is electrically connected to an FPC 508 via aconnector 215.

A light-emitting element 230 includes a lower electrode 231, an EL layer233, and an upper electrode 235. The lower electrode 231 is electricallyconnected to a source electrode or a drain electrode of a transistor240. An end portion of the lower electrode 231 is covered with theinsulating layer 211. The light-emitting element 230 has a top emissionstructure. The upper electrode 235 has a light-transmitting property andtransmits light emitted from the EL layer 233.

The coloring layer 259 is provided to overlap with the light-emittingelement 230, and the light-blocking layer 257 is provided to overlapwith the insulating layer 211. The coloring layer 259 and thelight-blocking layer 257 are covered with the insulating layer 261. Thespace between the light-emitting element 230 and the insulating layer261 is filled with the sealing layer 213.

The light-emitting panel includes a plurality of transistors in a lightextraction portion 504 and a driver circuit portion 506. The transistor240 is provided over the insulating layer 205. The insulating layer 205and the substrate 201 are attached to each other with the bonding layer203. The insulating layer 255 and the substrate 503 are attached to eachother with the bonding layer 505. It is preferable to use films with lowwater permeability for the insulating layer 205 and the insulating layer255, in which case an impurity such as water can be prevented fromentering the light-emitting element 230 or the transistor 240, leadingto improved reliability of the light-emitting panel. The bonding layer203 can be formed using a material similar to that of the bonding layer505.

The light-emitting panel in Specific Example 1 can be manufactured inthe following manner: the insulating layer 205, the transistor 240, andthe light-emitting element 230 are formed over a formation substratewith high heat resistance; the formation substrate is separated; and theinsulating layer 205, the transistor 240, and the light-emitting element230 are transferred to the substrate 201 and attached thereto with thebonding layer 203. The light-emitting panel in Specific Example 1 can bemanufactured in the following manner: the insulating layer 255, thecoloring layer 259, and the light-blocking layer 257 are formed over aformation substrate with high heat resistance; the formation substrateis separated; and the insulating layer 255, the coloring layer 259, andthe light-blocking layer 257 are transferred to the substrate 503 andattached thereto with the bonding layer 505.

In the case where a material with high water permeability and low heatresistance (e.g., resin) is used for a substrate, it is impossible toexpose the substrate to high temperature in the manufacturing process.Thus, there is a limitation on conditions for forming a transistor andan insulating film over the substrate. In the manufacturing method ofthis embodiment, a transistor and the like can be formed over aformation substrate with high heat resistance, thus, a highly reliabletransistor and an insulating film with sufficiently low waterpermeability can be formed. Then, the transistor and the insulating filmare transferred to the substrate 503 and the substrate 201, whereby ahighly reliable light-emitting panel can be manufactured. Thus,according to one embodiment of the present invention, a thin and/orlightweight and highly reliable light-emitting device can be provided.Details of the manufacturing method will be described later.

The substrate 503 and the substrate 201 are each preferably formed usinga material with high toughness. In that case, a display device with highimpact resistance that is less likely to be broken can be provided. Forexample, when the substrate 503 is an organic resin substrate and thesubstrate 201 is a substrate formed using a thin metal material or athin alloy material, the light-emitting panel can be more lightweightand less likely to be broken as compared with the case where a glasssubstrate is used.

A metal material and an alloy material, which have high thermalconductivity, are preferable because they can easily conduct heat to thewhole substrate and accordingly can prevent a local temperature rise inthe light-emitting panel. The thickness of a substrate using a metalmaterial or an alloy material is preferably greater than or equal to 10μm and less than or equal to 200 μm, further preferably greater than orequal to 20 μm and less than or equal to 50 μm.

Furthermore, when a material with high thermal emissivity is used forthe substrate 201, the surface temperature of the light-emitting panelcan be prevented from rising, leading to prevention of breakage or adecrease in reliability of the light-emitting panel. For example, thesubstrate 201 may have a stacked-layer structure of a metal substrateand a layer with high thermal emissivity (e.g., the layer can be formedusing a metal oxide or a ceramic material).

SPECIFIC EXAMPLE 2

FIG. 10A illustrates another example of the light extraction portion 504in the light-emitting panel. The light-emitting panel illustrated inFIG. 10A is capable of touch operation. In the following specificexamples, description of components similar to those in Specific Example1 is omitted.

The light-emitting panel illustrated in FIG. 10A includes the elementlayer 501, the bonding layer 505, and the substrate 503. The elementlayer 501 includes the substrate 201, the bonding layer 203, theinsulating layer 205, a plurality of transistors, the insulating layer207, the insulating layer 209, a plurality of light-emitting elements,the insulating layer 211, an insulating layer 217, the sealing layer213, the insulating layer 261, the coloring layer 259, thelight-blocking layer 257, a plurality of light-receiving elements, aconductive layer 281, a conductive layer 283, an insulating layer 291,an insulating layer 293, an insulating layer 295, and the insulatinglayer 255.

Specific Example 2 includes the insulating layer 217 over the insulatinglayer 211. The space between the substrate 503 and the substrate 201 canbe adjusted with the insulating layer 217.

FIG. 10A illustrates an example in which a light-receiving element isprovided between the insulating layer 255 and the sealing layer 213.Since the light-receiving element can be placed to overlap with anon-light-emitting region (e.g., a region where the transistor 240 or awiring is provided) on the substrate 201 side, the light-emitting panelcan be provided with a touch sensor without a decrease in the apertureratio of a pixel (light-emitting element).

As the light-receiving element included in the light-emitting panel, forexample, a p-n photodiode or a p-i-n photodiode can be used. In thisembodiment, a pin photodiode including a p-type semiconductor layer 271,an i-type semiconductor layer 273, and an n-type semiconductor layer 275is used as the light-receiving element.

Note that the i-type semiconductor layer 273 is a semiconductor in whichthe concentration of each of an impurity imparting p-type conductivityand an impurity imparting n-type conductivity is 1×10²⁰ atoms/cm³ orless and which has photoconductivity 100 times or more as high as darkconductivity. The i-type semiconductor layer 273 also includes, in itscategory, a semiconductor that contains an impurity element belonging toGroup 13 or Group 15 of the periodic table. In other words, since ani-type semiconductor has weak n-type electric conductivity when animpurity element for controlling valence electrons is not addedintentionally, the i-type semiconductor layer 273 includes, in itscategory, a semiconductor to which an impurity element imparting p-typeconductivity is added intentionally or unintentionally at the time ofdeposition or after the deposition.

The light-blocking layer 257 overlaps with the light-receiving elementon the side close to the substrate 503. The light-blocking layer 257between the light-receiving element and the sealing layer 213 canprevent the light-receiving element from being irradiated with lightemitted from the light-emitting element 230.

The conductive layer 281 and the conductive layer 283 are electricallyconnected to the light-receiving element. The conductive layer 281preferably transmits light incident on the light-receiving element. Theconductive layer 283 preferably blocks light incident on thelight-receiving element.

It is preferable to provide an optical touch sensor between thesubstrate 503 and the sealing layer 213 because the optical touch sensoris less likely to be affected by light emitted from the light-emittingelement 230 and can have improved S/N ratio.

SPECIFIC EXAMPLE 3

FIG. 10B illustrates another example of the light extraction portion 504in the light-emitting panel. The light-emitting panel illustrated inFIG. 10B is capable of touch operation.

The light-emitting panel illustrated in FIG. 10B includes the elementlayer 501, the bonding layer 505, and the substrate 503. The elementlayer 501 includes the substrate 201, the bonding layer 203, theinsulating layer 205, the plurality of transistors, the insulating layer207, an insulating layer 209 a, an insulating layer 209 b, the pluralityof light-emitting elements, the insulating layer 211, the insulatinglayer 217, the sealing layer 213, the coloring layer 259, thelight-blocking layer 257, the plurality of light-receiving elements, aconductive layer 280, the conductive layer 281, and the insulating layer255.

FIG. 10B illustrates an example in which a light-receiving element isprovided between the insulating layer 205 and the sealing layer 213.Since the light-receiving element is provided between the insulatinglayer 205 and the sealing layer 213, a conductive layer to which thelight-receiving element is electrically connected and a photoelectricconversion layer included in the light-receiving element can be formedusing the same materials and the same steps as a conductive layer and asemiconductor layer included in the transistor 240. Thus, thelight-emitting panel capable of touch operation can be manufacturedwithout a significant increase in the number of manufacturing steps.

SPECIFIC EXAMPLE 4

FIG. 11A illustrates another example of the light-emitting panel. Thelight-emitting panel illustrated in FIG. 11A is capable of touchoperation.

The light-emitting panel illustrated in FIG. 11A includes the elementlayer 501, the bonding layer 505, and the substrate 503. The elementlayer 501 includes the substrate 201, the bonding layer 203, theinsulating layer 205, the plurality of transistors, a conductive layer556, the conductive layer 557, the insulating layer 207, the insulatinglayer 209, the plurality of light-emitting elements, the insulatinglayer 211, the insulating layer 217, the sealing layer 213, the coloringlayer 259, the light-blocking layer 257, the insulating layer 255, aconductive layer 272, a conductive layer 274, an insulating layer 276,an insulating layer 278, a conductive layer 294, and a conductive layer296.

FIG. 11A illustrates an example in which a capacitive touch sensor isprovided between the insulating layer 255 and the sealing layer 213. Thecapacitive touch sensor includes the conductive layer 272 and theconductive layer 274.

The conductive layer 556 and the conductive layer 557 are electricallyconnected to the FPC 508 via the connector 215. The conductive layer 294and the conductive layer 296 are electrically connected to theconductive layer 274 via conductive particles 292. Thus, the capacitivetouch sensor can be driven via the FPC 508.

SPECIFIC EXAMPLE 5

FIG. 11B illustrates another example of the light-emitting panel. Thelight-emitting panel illustrated in FIG. 11B is capable of touchoperation.

The light-emitting panel illustrated in FIG. 11B includes the elementlayer 501, the bonding layer 505, and the substrate 503. The elementlayer 501 includes the substrate 201, the bonding layer 203, theinsulating layer 205, the plurality of transistors, the conductive layer556, the conductive layer 557, the insulating layer 207, the insulatinglayer 209, the plurality of light-emitting elements, the insulatinglayer 211, the insulating layer 217, the sealing layer 213, the coloringlayer 259, the light-blocking layer 257, the insulating layer 255, aconductive layer 270, the conductive layer 272, the conductive layer274, the insulating layer 276, and the insulating layer 278.

FIG. 11B illustrates an example in which a capacitive touch sensor isprovided between the insulating layer 255 and the sealing layer 213. Thecapacitive touch sensor includes the conductive layer 272 and theconductive layer 274.

The conductive layer 556 and the conductive layer 557 are electricallyconnected to an FPC 508 a via a connector 215 a. The conductive layer270 is electrically connected to an FPC 508 b via a connector 215 b.Thus, the light-emitting element 230 and the transistor 240 can bedriven via the FPC 508 a, and the capacitive touch sensor can be drivenvia the FPC 508 b.

SPECIFIC EXAMPLE 6

FIG. 12A illustrates another example of the light extraction portion 504in the light-emitting panel.

The light extraction portion 504 illustrated in FIG. 12A includes thesubstrate 503, the bonding layer 505, a substrate 202, the insulatinglayer 205, the plurality of transistors, the insulating layer 207, aconductive layer 208, the insulating layer 209 a, the insulating layer209 b, the plurality of light-emitting elements, the insulating layer211, the sealing layer 213, and the coloring layer 259.

The light-emitting element 230 includes the lower electrode 231, the ELlayer 233, and the upper electrode 235. The lower electrode 231 iselectrically connected to a source electrode or a drain electrode of thetransistor 240 with the conductive layer 208 provided therebetween. Anend portion of the lower electrode 231 is covered with the insulatinglayer 211. The light-emitting element 230 has a bottom emissionstructure. The lower electrode 231 has a light-transmitting property andtransmits light emitted from the EL layer 233.

The coloring layer 259 is provided to overlap with the light-emittingelement 230, and light emitted from the light-emitting element 230 isextracted from the substrate 503 side through the coloring layer 259.The space between the light-emitting element 230 and the substrate 202is filled with the sealing layer 213. The substrate 202 can be formedusing a material similar to that of the substrate 201.

Note that the touch sensor may be provided over a different substratefrom the substrate 503 and the substrate 201. As an example, FIG. 19Aillustrates an example in which a touch panel 999 is provided over thesubstrate 503. FIG. 19B illustrates an example in which the touch panel999 is provided under the substrate 201. The touch panel 999 is providedwith a plurality of electrodes and can operate as a capacitive touchsensor.

SPECIFIC EXAMPLE 7

FIG. 12B illustrates another example of the light-emitting panel.

The light-emitting panel illustrated in FIG. 12B includes the elementlayer 501, the bonding layer 505, and the substrate 503. The elementlayer 501 includes the substrate 202, the insulating layer 205, aconductive layer 310 a, a conductive layer 310 b, the plurality oflight-emitting elements, the insulating layer 211, a conductive layer212, and the sealing layer 213.

The conductive layer 310 a and the conductive layer 310 b, which areexternal connection electrodes of the light-emitting panel, can each beelectrically connected to an FPC or the like.

The light-emitting element 230 includes the lower electrode 231, the ELlayer 233, and the upper electrode 235. An end portion of the lowerelectrode 231 is covered with the insulating layer 211. Thelight-emitting element 230 has a bottom emission structure. The lowerelectrode 231 has a light-transmitting property and transmits lightemitted from the EL layer 233. The conductive layer 212 is electricallyconnected to the lower electrode 231.

The substrate 503 may have, as a light extraction structure, ahemispherical lens, a micro lens array, a film provided with an unevensurface structure, a light diffusing film, or the like. For example, thesubstrate 503 with a light extraction structure can be formed byattaching the above lens or film to a resin substrate with an adhesiveor the like having substantially the same refractive index as thesubstrate, or the lens or film.

The conductive layer 212 is preferably, though not necessarily, providedbecause voltage drop due to the resistance of the lower electrode 231can be prevented. In addition, for a similar purpose, a conductive layerelectrically connected to the upper electrode 235 may be provided overthe insulating layer 211.

The conductive layer 212 can be a single layer or a stacked layer formedusing a material selected from copper, titanium, tantalum, tungsten,molybdenum, chromium. neodymium, scandium, nickel, or aluminum, or analloy material containing any of these materials as its main component.The thickness of the conductive layer 212 can be greater than or equalto 0.1 μm and less than or equal to 3 μm, preferably greater than orequal to 0.1 μm and less than or equal to 0.5 μm.

When a paste (e.g., silver paste) is used as a material for theconductive layer electrically connected to the upper electrode 235,metal particles forming the conductive layer aggregate; therefore, thesurface of the conductive layer is rough and has many gaps. Thus, it isdifficult for the EL layer 233 to completely cover the conductive layer;accordingly, the upper electrode and the conductive layer are preferablyelectrically connected to each other easily.

[Examples of Materials]

Next, materials and the like that can be used for a light-emitting panelare described. Note that description on the components already describedin this embodiment is omitted.

The element layer 501 includes at least a light-emitting element. As thelight-emitting element, a self-luminous element can be used, and anelement whose luminance is controlled by current or voltage is includedin the category of the light-emitting element. For example, alight-emitting diode (LED), an organic EL element, an inorganic ELelement, or the like can be used.

The element layer 501 may further include a transistor for driving thelight-emitting element, a touch sensor, or the like.

The structure of the transistors in the light-emitting panel is notparticularly limited. For example, a forward staggered transistor or aninverted staggered transistor may be used. A top-gate transistor or abottom-gate transistor may be used. A semiconductor material used forthe transistors is not particularly limited, and for example, silicon orgermanium can be used. Alternatively, an oxide semiconductor containingat least one of indium, gallium, and zinc, such as an In-Ga-Zn-basedmetal oxide, may be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

The light-emitting element included in the light-emitting panel includesa pair of electrodes (the lower electrode 231 and the upper electrode235); and the EL layer 233 between the pair of electrodes. One of thepair of electrodes functions as an anode and the other functions as acathode.

The light-emitting element may have any of a top emission structure, abottom emission structure, and a dual emission structure. A conductivefilm that transmits visible light is used as the electrode through whichlight is extracted. A conductive film that reflects visible light ispreferably used as the electrode through which light is not extracted.

The conductive film that transmits visible light can be formed using,for example, indium oxide, indium tin oxide (ITO), indium zinc oxide,zinc oxide, or zinc oxide to which gallium is added. Alternatively, afilm of a metal material such as gold, silver, platinum, magnesium,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,or titanium; an alloy containing any of these metal materials; or anitride of any of these metal materials (e.g., titanium nitride) can beformed thin so as to have a light-transmitting property. Alternatively,a stack of any of the above materials can be used as the conductivelayer. For example, a stacked film of ITO and an alloy of silver andmagnesium is preferably used, in which case conductivity can beincreased. Further alternatively, graphene or the like may be used.

For the conductive film that reflects visible light, for example, ametal material such as aluminum, gold, platinum, silver, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or analloy including any of these metal materials can be used. Lanthanum,neodymium, germanium, or the like may be added to the metal material orthe alloy. Furthermore, an alloy containing aluminum (an aluminum alloy)such as an alloy of aluminum and titanium, an alloy of aluminum andnickel, or an alloy of aluminum and neodymium; or an alloy containingsilver such as an alloy of silver and copper, an alloy of silver,copper, and palladium, or an alloy of silver and magnesium can be usedfor the conductive film. An alloy of silver and copper is preferablebecause of its high heat resistance. Moreover, a metal film or a metaloxide film is stacked on an aluminum alloy film, whereby oxidation ofthe aluminum alloy film can be suppressed. Examples of a material forthe metal film or the metal oxide film are titanium and titanium oxide.Alternatively, the conductive film having a property of transmittingvisible light and a film containing any of the above metal materials maybe stacked. For example, a stacked film of silver and ITO or a stackedfilm of an alloy of silver and magnesium and ITO can be used.

The electrodes may be formed separately by an evaporation method or asputtering method. Alternatively, a discharging method such as an inkjet method, a printing method such as a screen printing method, or aplating method may be used.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the lower electrode 231 and the upperelectrode 235, holes are injected to the EL layer 233 from the anodeside and electrons are injected to the EL layer 233 from the cathodeside. The injected electrons and holes are recombined in the EL layer233 and a light-emitting substance contained in the EL layer 233 emitslight.

The EL layer 233 includes at least a light-emitting layer. In additionto the light-emitting layer, the EL layer 233 may further include one ormore layers containing any of a substance with a high hole-injectionproperty, a substance with a high hole-transport property, ahole-blocking material, a substance with a high electron-transportproperty, a substance with a high electron-injection property, asubstance with a bipolar property (a substance with a high electron- andhole-transport property), and the like.

For the EL layer 233, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may also beused. Each of the layers included in the EL layer 233 can be formed byany of the following methods: an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an ink-jetmethod, a coating method, and the like.

In the element layer 501, the light-emitting element is preferablyprovided between a pair of insulating films with low water permeability.Thus, an impurity such as water can be prevented from entering thelight-emitting element, leading to prevention of a decrease in thereliability of the light-emitting device.

As an insulating film with low water permeability, a film containingnitrogen and silicon such as a silicon nitride film or a silicon nitrideoxide film, a film containing nitrogen and aluminum such as an aluminumnitride film, or the like can be used. Alternatively, a silicon oxidefilm, a silicon oxynitride film, an aluminum oxide film, or the like canbe used.

For example, the water vapor transmittance of the insulating film withlow water permeability is lower than or equal to 1×10⁻⁵ [g/m²·day],preferably lower than or equal to 1×10⁻⁶ [g/m²·day], further preferablylower than or equal to 1×10⁻⁷ [g/m²·day], still further preferably lowerthan or equal to 1×10⁻⁸ [g/m²·day].

The substrate 503 has a light-transmitting property and transmits atleast light emitted from the element layer 501. Furthermore, thesubstrate 503 may be a flexible substrate. The refractive index of thesubstrate 503 is higher than that of the air.

An organic resin, which is lightweight than glass, is preferably usedfor the substrate 503, in which case the light-emitting device can bemore lightweight as compared with the case where glass is used.

Examples of a material having flexibility and a light-transmittingproperty with respect to visible light include glass that is thin enoughto have flexibility, polyester resins such as polyethylene terephthalate(PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, apolyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC)resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefinresin, a polystyrene resin, a polyamide imide resin, and a polyvinylchloride resin. In particular, a material whose thermal expansioncoefficient is low is preferable, and for example, a polyamide imideresin, a polyimide resin, or PET can be suitably used. A substrate inwhich a glass fiber is impregnated with an organic resin or a substratewhose thermal expansion coefficient is reduced by mixing an organicresin with an inorganic tiller can also be used.

The substrate 503 may have a stacked-layer structure in which a hardcoat layer (e.g, a silicon nitride layer) by which a surface of alight-emitting device is protected from damage, a layer (e.g., an aramidresin layer) which can disperse pressure, or the like is stacked over alayer of any of the above-described materials. Furthermore, to suppressa decrease in the lifetime of the light-emitting element due to moistureand the like, the insulating film with low water permeability may beincluded in the stacked-layer structure.

The bonding layer 505 has a light-transmitting property and transmits atleast light emitted from the light-emitting element included in theelement layer 501. The refractive index of the bonding layer 505 ishigher than that of the air.

For the bonding layer 505, a resin that is curable at room temperaturesuch as a two-component-mixture type resin, a light-curable resin, aheat-curable resin, or the like can be used. The examples include anepoxy resin, an acrylic resin, a silicone resin, and a phenol resin. Inparticular, a material with low moisture permeability, such as an epoxyresin, is preferable.

Furthermore, the above resin may include a drying agent. As the dryingagent, for example, a substance which adsorbs moisture by chemicaladsorption, such as an oxide of an alkaline earth metal (e.g., calciumoxide or barium oxide), can be used. Alternatively, a substance thatadsorbs moisture by physical adsorption, such as zeolite or silica gel,may be used. The drying agent is preferably included because it canprevent an impurity such as moisture from entering the light-emittingelement, thereby improving the reliability of the light-emitting device.

In addition, it is preferable to mix a filler with a high refractiveindex (e.g., titanium oxide) into the resin, in which case theefficiency of light extraction from the light-emitting element can beimproved.

The bonding layer 505 may also include a scattering member forscattering light. For example, the bonding layer 505 can be a mixture ofthe resin and particles having a refractive index different from that ofthe resin. The particles function as the scattering member forscattering light.

The difference in refractive index between the resin and the particleswith a refractive index different from that of the resin is preferably0.1 or more, further preferably 0.3 or more, Specifically, an epoxyresin, an acrylic resin, an imide resin, silicone, or the like can beused as the resin, and titanium oxide, barium oxide, zeolite, or thelike can be used as the particles.

Particles of titanium oxide or barium oxide are preferable because theyscatter light excellently. When zeolite is used, it can adsorb watercontained in the resin and the like, thereby improving the reliabilityof the light-emitting element.

The insulating layer 205 and the insulating layer 255 each can be formedusing an inorganic insulating material. It is particularly preferable touse the insulating film with low water permeability, in which case ahighly reliable light-emitting panel can be provided.

The insulating layer 207 has an effect of preventing diffusion ofimpurities into a semiconductor included in the transistor. As theinsulating layer 207, an inorganic insulating film such as a siliconoxide film, a silicon oxynitride film, or an aluminum oxide film can beused.

As each of the insulating layers 209, 209 a, and 209 b, an insulatingfilm with a planarization function is preferably selected in order toreduce surface unevenness due to the transistor or the like. Forexample, an organic material such as a polyimide resin, an acrylicresin, or a benzocyclobutene-based resin can be used. As an alternativeto such an organic material, a low-dielectric constant material (a low-kmaterial) or the like can be used. Note that a plurality of insulatingfilms formed of these materials or inorganic insulating films may bestacked.

The insulating layer 211 is provided to cover an end portion of thelower electrode 231. In order that the insulating layer 211 be favorablycovered with the EL layer 233 and the upper electrode 235 formedthereover, a side wall of the insulating layer 211 preferably has atilted surface with continuous curvature.

As a material for the insulating layer 211, a resin or an inorganicinsulating material can be used. As the resin, for example, a polyimideresin, a polyamide resin, an acrylic resin, a siloxane resin, an epoxyresin, or a phenol resin can be used. In particular, either a negativephotosensitive resin or a positive photosensitive resin is preferablyused for easy formation of the insulating layer 211.

There is no particular limitation on the method for forming theinsulating layer 211; a photolithography method, a sputtering method, anevaporation method, a droplet discharge method (e.g., an ink-jetmethod), a printing method (e.g., a screen printing method or an off-setpriming method), or the like may be used.

The insulating layer 217 can be formed using an inorganic insulatingmaterial, an organic insulating material, a metal material, or the like.As the organic insulating material, for example, a negative or positivephotosensitive resin or a non-photosensitive resin can be used. As themetal material, titanium, aluminum, or the like can be used. When aconductive material is used for the insulating layer 217 and theinsulating layer 217 is electrically connected to the upper electrode235, voltage drop due to the resistance of the upper electrode 235 canbe suppressed. The insulating layer 217 may have either a tapered shapeor an inverse tapered shape.

Each of the insulating layers 276, 278, 291, 293, and 295 can be formedusing an inorganic insulating material or an organic insulatingmaterial. It is particularly preferable to use an insulating film with aplanarization function for each of the insulating layers 278 and 295 inorder to reduce surface unevenness due to a sensor element.

For the sealing layer 213, a resin that is curable at room temperaturesuch as a two-component-mixture-type resin, a light-curable resin, aheat-curable resin, or the like can be used. For example, a polyvinylchloride (PVC) resin, an acrylic resin, a polyimide resin, an epoxyresin, a silicone resin, a polyvinyl butyral (PVB) resin, an ethylenevinyl acetate (EVA) resin, or the like can be used. A drying agent maybe contained in the sealing layer 213. In the case where light emittedfrom the light-emitting element 230 is extracted outside thelight-emitting panel through the sealing layer 213, the sealing layer213 preferably includes a filler with a high refractive index or ascattering member. Materials for the drying agent, the filler with ahigh refractive index, and the scattering member are similar to thosethat can be used for the bonding layer 505.

Each of the conductive layers 556, 557, 294, and 296 can be formed usingthe same material and the same step as a conductive layer included inthe transistor or the light-emitting element. The conductive layer 280can be formed using the same material and the same step as a conductivelayer included in the transistor.

For example, each of the conductive layers can be formed to have asingle-layer structure or a stacked-layer structure using any of metalmaterials such as molybdenum, titanium, chromium, tantalum, tungsten,aluminum, copper, neodymium, and scandium, and an alloy materialcontaining any of these elements. Each of the conductive layers may beformed using a conductive metal oxide. As the conductive metal oxide,indium oxide (e.g., In₂O₃), tin oxide (e.g., SnO₂), zinc oxide (ZnO),ITO, indium zinc oxide (e.g., In₂O₃—ZnO), or any of these metal oxidematerials in which silicon oxide is contained can be used.

Each of the conductive layers 208, 212, 310 a, and 310 b can also beformed using any of the above metal materials, alloy materials, andconductive metal oxides.

Each of the conductive layers 272, 274, 281, and 283 is a conductivelayer with a light-transmitting property. The conductive layer can beformed using, for example, indium oxide, ITO, indium zinc oxide, zincoxide, zinc oxide to which gallium is added, or the like. The conductivelayer 270 can be formed using the same material and the same step as theconductive layer 272.

As the conductive particles 292, particles of an organic resin, silica,or the like coated with a metal material are used. It is preferable touse nickel or gold as the metal material because contact resistance canbe decreased. It is also preferable to use particles each coated withlayers of two or more kinds of metal materials, such as particles coatedwith nickel and further with gold.

For the connector 215, it is possible to use a paste-like or sheet-likematerial which is obtained by mixture of metal particles or particlessimilar to the above conductive particles with a thermosetting resin andfor which anisotropic electric conductivity is provided bythermocompression bonding. As the metal particles, particles in whichtwo or more kinds of metals are layered, for example, nickel particlescoated with gold are preferably used.

The coloring layer 259 is a colored layer that transmits light in aspecific wavelength range. For example, a red (R) color filter fortransmitting light in a red wavelength range, a green (G) color filterfor transmitting light in a green wavelength range, a blue (B) colorfilter for transmitting light in a blue wavelength range, or the likecan be used. Each coloring layer is formed in a desired position withany of various materials by a printing method, an ink-jet method, anetching method using a photolithography method, or the like.

The light-blocking layer 257 is provided between the adjacent coloringlayers 259. The light-blocking layer 257 blocks light emitted from theadjacent light-emitting element, thereby preventing color mixturebetween adjacent pixels. Here, the coloring layer 259 is provided suchthat its end portion overlaps with the light-blocking layer 257, wherebylight leakage can be reduced. The light-blocking layer 257 can be formedusing a material that blocks light emitted from the light-emittingelement, for example, a metal material, a resin material including apigment or a dye, or the like. Note that as illustrated in FIG. 9A, thelight-blocking layer 257 is preferably provided also in a region otherthan the light extraction portion 504, such as the driver circuitportion 506, in which case undesired leakage of guided light or the likecan be suppressed.

The insulating layer 261 covering the coloring layer 259 and thelight-blocking layer 257 is preferably provided because it can preventan impurity such as a pigment included in the coloring layer 259 or thelight-blocking layer 257 from diffusing into the light-emitting elementor the like. For the insulating layer 261, a light-transmitting materialis used, and an inorganic insulating material or an organic insulatingmaterial can be used. The insulating film with low water permeabilitymay be used for the insulating layer 261.

The above is the description of the examples on materials.

[Example of Manufacturing Method]

Next, an example of a method for manufacturing a light-emitting panel isdescribed with reference to FIGS. 13A to 13C and FIGS. 14A to 14C. Here,the manufacturing method is described using the light-emitting panel ofSpecific Example 1 (FIG. 9B) as an example.

First, a separation layer 303 is formed over a formation substrate 301,and the insulating layer 205 is formed over the separation layer 303.Next, the plurality of transistors, the conductive layer 557, theinsulating layer 207, the insulating layer 209, the plurality oflight-emitting elements, and the insulating layer 211 are formed overthe insulating layer 205. An opening is formed in the insulating layers211, 209, and 207 to expose the conductive layer 557 (FIG. 13A).

In addition, a separation layer 307 is formed over a formation substrate305, and the insulating layer 255 is formed over the separation layer307. Next, the light-blocking layer 257, the coloring layer 259, and theinsulating layer 261 are formed over the insulating layer 255 (FIG.13B).

The formation substrate 301 and the formation substrate 305 each can bea glass substrate, a quartz substrate, a sapphire substrate, a ceramicsubstrate, a metal substrate, or the like.

For the glass substrate, for example, a glass material such asaluminosilicate glass, aluminoborosilicate glass, or barium borosilicateglass can be used. When the temperature of the heat treatment performedlater is high, a substrate having a strain point of 730° C. or higher ispreferably used as the glass substrate. Note that by containing a largeamount of barium oxide (BaO), a glass substrate which is heat-resistantand more practical can be obtained. Alternatively, crystallized glass orthe like may be used.

In the case where a glass substrate is used as the formation substrate,an insulating film such as a silicon oxide film, a silicon oxynitridefilm, a silicon nitride film, or a silicon nitride oxide film ispreferably formed between the formation substrate and the separationlayer, in which case contamination from the glass substrate can beprevented.

The separation layer 303 and the separation layer 307 each have asingle-layer structure or a stacked-layer structure containing anelement selected from tungsten, molybdenum, titanium, tantalum, niobium,nickel, cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium,iridium, and silicon; an alloy material containing any of the elements;or a compound material containing any of the elements. A crystalstructure of a layer containing silicon may be amorphous, microcrystal,or polycrystal.

The separation layer can be formed by a sputtering method, a plasma CVDmethod, a coating method, a printing method, or the like. Note that acoating method includes a spin coating method, a droplet dischargemethod, and a dispensing method.

In the case where the separation layer has a single-layer structure, atungsten layer, a molybdenum layer, or a layer containing a mixture oftungsten and molybdenum is preferably formed. Alternatively, a layercontaining an oxide or an oxynitride of tungsten, a layer containing anoxide or an oxynitride of molybdenum, or a layer containing an oxide oran oxynitride of a mixture of tungsten and molybdenum may be formed.Note that a mixture of tungsten and molybdenum is an alloy of tungstenand molybdenum, for example.

In the case where the separation layer is formed to have a stacked-layerstructure including a layer containing tungsten and a layer containingan oxide of tungsten, the layer containing an oxide of tungsten may beformed as follows: the layer containing tungsten is formed first and aninsulating film formed of an oxide is formed thereover, so that thelayer containing an oxide of tungsten is formed at the interface betweenthe tungsten layer and the insulating film. Alternatively, the layercontaining an oxide of tungsten may be formed by performing thermaloxidation treatment, oxygen plasma treatment, nitrous oxide (N₂O) plasmatreatment, treatment with a highly oxidizing solution such as ozonewater, or the like on the surface of the layer containing tungsten.Plasma treatment or heat treatment may be performed in an atmosphere ofoxygen, nitrogen, or nitrous oxide alone, or a mixed gas of any of thesegasses and another gas. Surface condition of the separation layer ischanged by the plasma treatment or heat treatment, whereby adhesionbetween the separation layer and the insulating film formed later can becontrolled.

Each of the insulating layers can be formed by a sputtering method, aplasma CVD method, a coating method, a printing method, or the like. Forexample, the insulating layer is formed at a temperature higher than orequal to 250° C. and lower than or equal to 400° C. by a plasma CVDmethod, whereby the insulating layer can be a dense film with very lowwater permeability.

Then, a material for the sealing layer 213 is applied to a surface ofthe formation substrate 305 over which the coloring layer 259 and thelike are formed or a surface of the formation substrate 301 over whichthe light-emitting element 230 and the like are formed, and theformation substrate 301 and the formation substrate 305 are attached sothat these two surfaces face each other with the sealing layer 213provided therebetween (FIG. 13C).

Next, the formation substrate 301 is separated, and the exposedinsulating layer 205 and the substrate 201 are attached to each otherwith the bonding layer 203. Furthermore, the formation substrate 305 isseparated, and the exposed insulating layer 255 and the substrate 503are attached to each other with the bonding layer 505. Although thesubstrate 503 does not overlap with the conductive layer 557 in FIG.14A, the substrate 503 may overlap with the conductive layer 557.

Any of a variety of methods can be used as appropriate for theseparation process. For example, when a layer including a metal oxidefilm is formed as the separation layer on the side in contact with thelayer to be separated, the metal oxide film is embrittled bycrystallization, whereby the layer to be separated can be separated fromthe formation substrate. Alternatively, when an amorphous silicon filmcontaining hydrogen is formed as the separation layer between aformation substrate having high heat resistance and a layer to beseparated, the amorphous silicon film is removed by laser lightirradiation or etching, whereby the layer to be separated can beseparated from the formation substrate. Alternatively, after a layerincluding a metal oxide film is formed as the separation layer on theside in contact with the layer to be separated, the metal oxide film isembrittled by crystallization, and part of the separation layer isremoved by etching using a solution or a fluoride gas such as NF₃, BrF₃,or ClF₃, whereby the separation can be performed at the embrittled metaloxide film. Further alternatively, a method carried out as follows maybe employed: a film containing nitrogen, oxygen, hydrogen, or the like(e.g., an amorphous silicon film containing hydrogen, an alloy filmcontaining hydrogen, or an alloy film containing oxygen) is used as theseparation layer, and the separation layer is irradiated with laserlight to release the nitrogen, oxygen, or hydrogen contained in theseparation layer as gas, thereby promoting separation between the layerto be separated and the formation substrate. Still furtheralternatively, it is possible to use a method in which the formationsubstrate provided with the layer to be separated is removedmechanically or by etching using a solution or a fluoride gas such asNF₃, BrF₃, or ClF₃, or the like, in this case, the separation layer isnot necessarily provided.

When a plurality of the above-described separation methods are combined,the separation process can be performed easily. In other words,separation can be performed with physical force (by a machine or thelike) after performing laser light irradiation, etching on theseparation layer with a gas, a solution, or the like, or mechanicalremoval with a sharp knife, scalpel or the like so that the separationlayer and the layer to be separated can be easily separated from eachother.

Separation of the layer to be separated from the formation substrate maybe performed by soaking the interface between the separation layer andthe layer to be separated in a liquid. Furthermore, the separation maybe performed while a liquid such as water is being poured.

As another separation method, in the case where the separation layer isformed using tungsten, it is preferable that the separation be performedwhile etching the separation layer using a mixed solution of ammoniumwater and a hydrogen peroxide solution.

Note that the separation layer is not necessarily provided in the casewhere separation at an interface between the formation substrate and thelayer to be separated is possible. For example, glass is used as theformation substrate, an organic resin such as polyimide is formed incontact with the glass, and an insulating film, a transistor, and thelike are formed over the organic resin. In this case, heating theorganic resin enables the separation at the interface between theformation substrate and the organic resin. Alternatively, separation atthe interface between a metal layer and the organic resin may beperformed in the following manner: the metal layer is provided betweenthe formation substrate and the organic resin and current is made toflow in the metal layer so that the metal layer is heated.

Lastly, an opening is formed in the insulating layer 255 and the sealinglayer 213 to expose the conductive layer 557 (FIG. 14B). In the casewhere the substrate 503 overlaps with the conductive layer 557, anopening is formed also in the substrate 503 and the bonding layer 505(FIG. 14C). The method for forming the opening is not particularlylimited and may be, for example, a laser ablation method, an etchingmethod, an ion beam sputtering method, or the like. As another method, acut may be made in a film over the conductive layer 557 with a sharpknife or the like and part of the film may be separated by physicalforce.

In the above-described manner, the light-emitting panel can bemanufactured.

As described above, the light-emitting panel of this embodiment includestwo substrates; one is the substrate 503 and the other is the substrate201 or the substrate 202. The light-emitting device can be formed withtwo substrates even when including a touch sensor. Owing to the use ofthe minimum number of substrates, improvement in light extractionefficiency and improvement in clarity of display can be easily achieved.

MODIFICATION EXAMPLE

A light-emitting panel which is partly different from the abovelight-emitting panel is described below with reference to FIG. 15.

A light-emitting panel illustrated in FIG. 15 includes a substrate 401,the transistor 240, the light-emitting element 230, the insulating layer207, the insulating layer 209, the insulating layer 211, the insulatinglayer 217, a space 405, the insulating layer 261, the light-blockinglayer 257, the coloring layer 259, a light-receiving element (includingthe p-type semiconductor layer 271, the i-type semiconductor layer 273,and the n-type semiconductor layer 275), the conductive layer 281, theconductive layer 283, the insulating layer 291, the insulating layer293, the insulating layer 295, and a substrate 403.

The light-emitting panel includes a bonding layer (not illustrated)formed in a frame shape between the substrate 401 and the substrate 403to surround the light-emitting element 230 and the light-receivingelement. The light-emitting element 230 is sealed by the bonding layer,the substrate 401, and the substrate 403.

In the light-emitting panel of this embodiment, the substrate 403 has alight-transmitting property. Light emitted from the light-emittingelement 230 is extracted to the air through the coloring layer 259, thesubstrate 403, and the like.

The light-emitting panel of this embodiment is capable of touchoperation. Specifically, proximity or contact of an object on a surfaceof the substrate 403 can be sensed with the light-receiving element.

An optical touch sensor is highly durable and preferable because itssensing accuracy is not affected by damage to a surface that is touchedby an object. An optical touch sensor is also advantageous in that it iscapable of noncontact sensing, it does not degrade the clarity of imageseven when used in a display device, and it is applicable to large-sizedlight-emitting panels and display devices.

It is preferable to provide an optical touch sensor between thesubstrate 403 and the space 405 because the optical touch sensor is lesslikely to be affected by light emitted from the light-emitting element230 and can have improved S/N ratio.

The light-blocking layer 257 overlaps with the light-receiving elementon the side close to the substrate 403. The light-blocking layer 257 canprevent the light-receiving element from being irradiated with lightemitted from the light-emitting element 230.

There is no particular limitation on materials used for the substrates401 and 403. The substrate on the side from which light from thelight-emitting element is extracted is formed using a material whichtransmits the light. For example, a material such as glass, quartz,ceramics, sapphire, or an organic resin, which is thin enough to haveflexibility, can be used. Furthermore, since the substrate through whichlight emission is not extracted does not need to have alight-transmitting property, a metal substrate using a metal material oran alloy material or the like can be used in addition to theabove-mentioned substrates. In addition, any of the materials for thesubstrates given in the above embodiments can also be used for thesubstrates 401 and 403.

A method fir sealing the light-emitting panel is not limited, and eithersolid sealing or hollow sealing can be employed. For example, a glassmaterial such as a glass fit, or a resin material that is curable atroom temperature such as a two-component-mixture-type resin, a lightcurable resin, a thermosetting resin, or the like can be used. The space405 may be filled with an inert gas such as nitrogen or argon, or with aresin or the like similar to that used for the sealing layer 213.Furthermore, the resin may include the drying agent, the filler with ahigh refractive index, or the scattering member.

At least part of this embodiment can be implemented as appropriate incombination with any of the other embodiments described in thisspecification.

Embodiment 3

In this embodiment, examples of an electronic device and a lightingdevice including the display device of one embodiment of the presentinvention will be described with reference to drawings.

As examples of electronic devices including a display device withflexibility, the following can be given: television devices (alsoreferred to as televisions or television receivers), monitors ofcomputers or the like, cameras such as digital cameras or digital videocameras, digital photo frames, mobile phones (also referred to as mobilephones or mobile phone devices), portable game machines, portableinformation terminals, audio reproducing devices, and large gamemachines such as pachinko machines.

In addition, a lighting device or a display device can be incorporatedalong a curved inside/outside wall surface of a house or a building or acurved interior/exterior surface of a car.

FIGS. 17A and 17B illustrate a two-foldable tablet terminal 9600. Notethat here, an example of the two-foldable tablet terminal isillustrated; however, a display device of one embodiment of the presentinvention can be employed for those having a large folding number suchas a tablet terminal foldable into three or four. In FIG. 17A, thetablet terminal 9600 is opened, and includes a housing 9630, a displayportion 9631, a switch 9626 for switching display modes, a power switch9627, a switch 9625 for switching to power-saving mode, a fastener 9629,and an operation switch 9628.

The housing 9630 includes a housing 9630 a and a housing 9630 b, and thehousing 9630 a and the housing 9630 b are combined with each other witha hinge portion 9639. The housing 9630 is two-foldable owing to thehinge portion 9639.

The display portion 9631 is provided on the housing 9630 a, the housing9630 b, and the hinge portion 9639. With the use of any of the displaydevices disclosed in this specification and the like as the displayportion 9631, the tablet terminal in which the display portion 9631 canbe bent and which has high reliability can be provided.

Part of the display portion 9631 can be a touch panel region 9632 anddata can be input when a displayed operation key panel 9638 is touched.Note that for example, half of the display portion 9631 can have only adisplay function and the other half thereof can have a touch panelfunction. Alternatively, the whole display portion 9631 may have a touchpanel function. For example, keyboard buttons can be displayed on theentire screen of the display portion 9631 so that the entire screen isused as a data input terminal.

The switch 9626 for switching a display mode allows switching between alandscape mode and a portrait mode, color display and black-and-whitedisplay, and the like.

The switch 9625 for switching to power-saving mode can control displayluminance to be optimal in accordance with the amount of external lightin use of the tablet terminal which is detected by an optical sensorincorporated in the tablet terminal. In addition to the optical sensor,other detecting devices such as sensors for determining inclination,such as a gyroscope or an acceleration sensor, may be incorporated inthe tablet terminal.

In FIG. 17B, the tablet terminal 9600 is closed, and includes thehousing 9630, a solar cell 9633, and a charge and discharge controlcircuit 9634. Note that FIG. 17B illustrates an example in which thecharge and discharge control circuit 9634 includes a battery 9635 and aDCDC converter 9636.

With the use of any of the display devices disclosed in thisspecification and the like for the display portion 9631, the displayportion 9631 can be folded. For example, since the tablet terminal 9600is two-foldable, the housing 9630 can be closed when the tablet terminalis not used. Thus, the display portion 9631 can be protected by closingthe housing 9630, whereby the tablet terminal 9600 can have highdurability and portability and thus can have improved reliability forlong-term use.

The tablet terminal illustrated in FIGS. 17A and 17B can have otherfunctions such as a function of displaying a variety of kinds of data(e.g., a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function of operating or editing the datadisplayed on the display portion by touch input, and a function ofcontrolling processing by a variety of kinds of software (programs).

The solar cell 9633, which is attached on the surface of the tabletterminal, supplies electric power to a touch panel, a display portion,an image signal processor, and the like. The solar cell 9633 can beprovided on at least one surface of the housing 9630 to charge thebattery 9635, which is favorable. When a lithium ion battery is used asthe batted 9635, there is an advantage of downsizing or the like.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 17B are described with reference to a blockdiagram of FIG. 17C. FIG. 17C illustrates the solar cell 9633, thebattery 9635, the DCDC converter 9636, a converter 9637, switches SW1 toSW3, and the display portion 9631. The battery 9635, the DCDC converter9636, the converter 9637, and the switches SW1 to SW3 correspond to thecharge and discharge control circuit 9634 in FIG. 17B.

First, an example of operation in the case where power is generated bythe solar cell 9633 using external light is described. The voltage ofpower generated by the solar cell is raised or lowered by the DCDCconverter 9636 so that a voltage for charging the battery 9635 isobtained. When the display portion 9631 is operated with the power fromthe solar cell 9633, the switch SW1 is turned on and the voltage of thepower is raised or lowered by the converter 9637 to a voltage needed foroperating the display portion 9631. In addition, when display on thedisplay portion 9631 is not performed, the switch SW1 is turned off anda switch SW2 is turned on so that charge of the battery 9635 may beperformed.

Here, the solar cell 9633 is shown as an example of a power generationmeans; however, there is no particular limitation on a way of chargingthe battery 9635, and the battery 9635 may be charged with another powergeneration means such as a piezoelectric element or a thermoelectricconversion element (Peltier element). For example, the battery 9635 maybe charged with a non-contact power transmission module capable ofperforming charging by transmitting and receiving electric powerwirelessly (without contact), or any of the other charge means used incombination.

It is needless to say that one embodiment of the present invention isnot limited to the above-described electronic devices and lightingdevices as long as the display device of one embodiment of the presentinvention is included.

At least part of this embodiment can be implemented as appropriate incombination with any of the other embodiments described in thisspecification.

This application is based on Japanese Patent Application serial No.2013-181758 filed with the Japan Patent Office on Sep. 3, 2013, theentire contents of which are hereby incorporated by reference.

What is claimed is:
 1. An electronic device comprising: a light-emittingpanel; a protection fixed to a back of the light-emitting panel; a firsthousing, which is less flexible than the light-emitting panel,overlapping with a first region of the light-emitting panel; a secondhousing, which is less flexible than the light-emitting panel,overlapping with a second region of the light emitting panel; and abending portion provided between the first housing and the secondhousing, wherein the light-emitting panel and the protection have aregion overlapping with the bending portion, wherein the electronicdevice is configured to be foldable by bending the bending portion,wherein the light-emitting panel is provided continuously from the firstregion to the second region, wherein the first region and the secondregion overlap each other, in a folded state of the electronic device,wherein, in an opened state of the electronic device, an image isdisplayed in the first region, the second region, and the region wherethe light-emitting panel overlaps the bending portion, wherein theelectronic device is configured to be bendable to an outside, wherein,in the folded state of the electronic device, the first region and theregion where the light-emitting panel overlaps the bending portion arevisible, wherein, in the folded state of the electronic device, theregion where the light-emitting panel overlaps the bending portion isconfigured to display an image, wherein the light-emitting panelcomprises a transistor comprising an oxide semiconductor layer, whereinthe oxide semiconductor layer comprises a channel formation region, andwherein the transistor is electrically connected to a light-emittingelement.
 2. An electronic device comprising: a light-emitting panel; aprotection fixed to a back of the light-emitting panel; a first housing,which is less flexible than the light-emitting panel, overlapping with afirst region of the light-emitting panel; a second housing, which isless flexible than the light-emitting panel, overlapping with a secondregion of the light emitting panel; and a bending portion providedbetween the first housing and the second housing, wherein thelight-emitting panel and the protection have a region overlapping withthe bending portion, wherein the electronic device is configured to befoldable by bending the bending portion, wherein the light-emittingpanel is provided continuously from the first region to the secondregion, wherein the first region and the second region overlap eachother, in a folded state of the electronic device, wherein, in an openedstate of the electronic device, an image is displayed in the firstregion, the second region, and the region where the light-emitting paneloverlaps the bending portion, wherein the electronic device isconfigured to be bendable to an outside, wherein, in the folded state ofthe electronic device, the first region and the region where thelight-emitting panel overlaps the bending portion are visible, wherein,in the folded state of the electronic device, the region where thelight-emitting panel overlaps the bending portion is configured todisplay an image, wherein the light-emitting panel comprises atransistor, and wherein the transistor is electrically connected to alight-emitting element.
 3. An electronic device comprising: alight-emitting panel; a protection fixed to a back of the light-emittingpanel; a first housing, which is less flexible than the light-emittingpanel, overlapping with a first region of the light-emitting panel; asecond housing, which is less flexible than the light-emitting panel,overlapping with a second region of the light emitting panel; and abending portion provided between the first housing and the secondhousing, wherein the light-emitting panel and the protection have aregion overlapping with the bending portion, wherein the electronicdevice is configured to be foldable by bending the bending portion,wherein the light-emitting panel is provided continuously from the firstregion to the second region, wherein the first region and the secondregion face each other, in a folded state of the electronic device,wherein, in an opened state of the electronic device, an image isdisplayed in the first region, the second region, and the region wherethe light-emitting panel overlaps the bending portion, and wherein theelectronic device is configured to be bendable to an inside.
 4. Theelectronic device according to claim 1, wherein a sensor configured todetermine whether the electronic device is in a folded state or not isprovided.
 5. The electronic device according to claim 2, wherein asensor configured to determine whether the electronic device is in afolded state or not is provided.
 6. The electronic device according toclaim 3, wherein the electronic device is configured to be foldable bybending the light-emitting panel and the protective layer in the regionwhere the light-emitting panel overlaps the bending portion, wherein asensor configured to determine whether the electronic device is in afolded state or not is provided, and wherein, in the folded state, thelight-emitting panel does not emit light.
 7. The electronic deviceaccording to claim 1, wherein the protection is provided between thefirst housing and the light-emitting panel.
 8. The electronic deviceaccording to claim 2, wherein the protection is provided between thefirst housing and the light-emitting panel.
 9. The electronic deviceaccording to claim 3, wherein the protection is provided between thefirst housing and the light-emitting panel.